package com.example.mcu_up.serial;

import android.util.Log;
 

public class CRC16 {
    private static short[] crcTable = new short[256];
    private static int gPloy = 0x8408; // 生成多项式

     private static short getCrcOfByte(int aByte) {
        int value = aByte << 8;

        for (int count = 7; count >= 0; count--) {
            if ((value & 0x8000) != 0) { // 高第16位为1，可以按位异或
                value = (value << 1) ^ gPloy;
            } else {
                value = value << 1; // 首位为0，左移
            }

        }
        value = value & 0xFFFF; // 取低16位的值
        return (short)value;
    }

    public static short getCrc(byte[] data) {
        int crc = 0;
        int length = data.length;
        
        for (int i = 0; i < 256; i++) {
            crcTable[i] = getCrcOfByte(i);
        }
        for (int i = 0; i < length; i++) {
            crc = ((crc & 0xFF) << 8) ^ crcTable[(((crc & 0xFF00) >> 8) ^ data[i]) & 0xFF];
        }
        crc = crc & 0xFFFF;
        return (short)crc;
    }
   
    public static short getCheckSum(byte[] data){
      short sum=0;
      int n=data.length-1;
      for(int i=0;i<n;i++){
    	  sum+=data[i];
      }
     return (short) (1 + ~sum);
    }
    public static  int CyBtldr_ComputeChecksumCrc16( byte[] buf,  int size)
    {
        
    	    int crc = (int) 0xffff;
    	    int tmp;
               
    	    if (size == 0)
    		    return (int) (~crc);

    	    int i = 0;
    	    int j = 0;
    	    do{
    		    for (i = 0, tmp = (int) (0x00ff&buf[j]); i < 8; i++,tmp >>= 1)
    		    {
    		        if (((crc & 0x0001)^(tmp&0x0001))!=0)
    				    crc = (int) ((crc >> 1) ^ 0x8408);
    			    else
    			        crc >>= 1;
    			        	;
    		    }
    		    j++;
    	    }while ( --size!= 0);
    	    
    	    crc = (int) (~crc & 0xFFFF);
    	     tmp = crc;
    	    crc = (int) ((crc << 8) | (tmp >> 8 & 0x00FF));
    	    return (int)crc&0x0000ffff;
    }
    
    
    
    public static  int CyBtldr_ComputeChecksum( byte[] buf,int size){
    	int sum = 0;
	    for(int i=0;i<size;i++)
		    sum += buf[i]&0x00ff;
    	
	      
	    Log.i("checksum",String.valueOf((int)(1 + ~sum)+0xffff));
	    return (int)((1 + ~sum));
	    
	    
	    
    }
    
    
}
